Showing papers on "Lepton published in 1985"
TL;DR: In this article, a numerical model based on hydrodynamics coupled to radiation transport of all neutrino types is developed for calculating stellar core collapse, including neutrinos.
Abstract: A numerical model based on hydrodynamics coupled to radiation transport of all neutrino types is developed for calculating stellar core collapse. General relativistic hydrodynamic equations for spherically symmetric systems including neutrino flow are obtained and presented in a form paralleling the adiabatic equations of May and White (1967). A multigroup, flux-limited diffusion scheme, used to evolve ..nu../sub e/'s, nu-bar/sub e/'s, and ..nu../sub ..mu../ and ..nu../sub tau/ pairs independently, is derived from the neutrino Boltzmann equation. Expressions for the zeroth and first Legendre moments of all important neutrino interactions are derived from the standard model of electroweak interactions. Numerical values are obtained from these expressions (by numerical integration when necessary) during core-collapse calculations. An implicit numerical scheme for directly solving the neutrino equations, including the neutrino-electron scattering and neutrino thermal production terms, is presented. This scheme includes a consistent treatment of neutrino-matter decoupling in the neutrino transparent regimes. At the present time, the equation of state of Lamb et al. (1978, 1981) up to nuclear density, and that of Friedman and Pandharipande (1981) above nucleon density, are incorporated in the numerical model.
704 citations
TL;DR: In this paper, simple expressions for continuum electron and positron capture phase space factors and the associated neutrino energy loss integrals are presented in terms of standard Fermi integrals.
Abstract: Simple expressions for continuum electron and positron capture phase space factors and the associated neutrino energy loss integrals are presented in terms of standard Fermi integrals. Continuous approximations to the relevant Fermi integrals and their first derivatives are made. These allow the computation of effective log (ft)--values, at each temperature and density point, for the continuum lepton capture rates considered in the earlier papers in this series. Since the effective log (ft)--values have most of the rapid temperature and density dependence associated with the phase space integrals removed, interpolation in temperature and density to obtain stellar rates is greatly facilitated in speed and accuracy. Computer simulations of stellar evolution will be able to implement more accurately our calculations of the stellar nuclear weak interaction rates of intermediate-mass nuclei. Generalization of the Fermi integral expressions for the lepton continuum capture phase space factors are given for astrophysical environments where there exists an equilibrium distribution of electron-type neutrinos. These allow rough estimates of the effect of neutrino blocking on our tabulated rates and estimates of total neutrino capture rates.
436 citations
01 Dec 1985
TL;DR: For small mixing angles in vacuum the enhancement displays a resonance behavior in the neutrino energies or the density of the medium as discussed by the authors, which leads to a strong suppression of neutrinos flux even for small sin/sup 2/ 2theta.
Abstract: Matter can enhance neutrino oscillations (increase the mixing parameter sin/sup 2/ 2theta/sub m/). For small mixing angles in vacuum the enhancement displays a resonance behavior in the neutrino energies or the density of the medium. This resonance effect is important for solar neutrinos in a wide range of oscillation parameters ..delta..m/sup 2/ = 10/sup -4/--10/sup -8/ eV/sup 2/ and sin/sup 2/ 2theta>10/sup -4/. It leads to a strong suppression of the neutrino flux even for small sin/sup 2/ 2theta.
366 citations
CERN1
TL;DR: In this paper, it was shown that in the limit ϵ → 0, both the forward-backward asymmetry in e + e − → τ + τ − and the τ lifetime are unchanged, and single production of (R -odd) sparticles may occur.
246 citations
TL;DR: The photino is a possible candidate particle; mirror neutrinos may also be candidates as discussed by the authors, but the photino has a scattering cross-section on protons of 4 x 10/sup -36/ cm/sup 2/
Abstract: A possible solution to the solar neutrino problem is to posit a massive, stable, neutral particle as part of the Sun's primordial composition. If that particle has a mass between 5 and 60 GeV, then it will populate only the inner ''solar neutrino unit-producing'' core and not the larger luminosity-producing region. If it has a scattering cross section on protons of 4 x 10/sup -36/ cm/sup 2/, then a fractional abundance of 10/sup -12/ will have order-unity effect on the Sun's thermal transport, in the direction of decreasing the expected neutrino signature. For smaller cross sections, the required abundance rises in inverse proportion, so that cross sections as small as 10/sup -46/ cm/sup 2/ are effective if the concentration is as large as approx.10/sup -2/. The photino is a possible candidate particle; mirror neutrinos may also be candidates.
214 citations
TL;DR: The observation of a distortion of the ..beta.. spectrum of tritium is reported, consistent with the emission of a neutrino of mass about 17.1 keV and a mixing probability of 3%.
Abstract: The observation of a distortion of the $\ensuremath{\beta}$ spectrum of tritium is reported. This distortion is consistent with the emission of a neutrino of mass about 17.1 keV and a mixing probability of 3%.
211 citations
TL;DR: A new and more sensitive search for oscillations of reactor antineutrinos is practical and would lay the groundwork for a more ambitious measurement of the spectrum pp, /sup 7/Be and /sup 8/B solar ..nu..'s, and supernovae anywhere in the authors' galaxy.
Abstract: Elastic neutrino scattering off electrons in crystalline silicon at 1-10 mK results in measurable temperature changes in macroscopic amounts of material, even for low-energy (less than 0.41-MeV) pp neutrinos from the sun. New detectors for bolometric measurement of low-energy neutrino interactions, including coherent nuclear elastic scattering, are proposed. A new and more sensitive search for oscillations of reactor antineutrinos is practical (about 100 kg of Si), and would lay the groundwork for a more ambitious measurement of the spectrum of pp, Be-7, and B-8 solar neutrinos, and of supernovae anywhere in the Galaxy (about 10 tons of Si).
165 citations
TL;DR: In this paper, a solar neutrino problem is considered and the present abundance of neutrinos is determined by balancing capture rates against annihilation rates in the Sun, based on a combination of particle physics and cosmological considerations.
Abstract: Certain currently proposed weakly interacting elementary particles can have a high probability of solar capture if they make up the Galactic halo. Their present abundance in the Sun is here determined by balancing capture rates against annihilation rates. Both particle physics and cosmological considerations impose constraints on scattering and annihilation cross sections. In general, for the candidate particles here discussed (massive neutrinos, supersymmetric scalar neutrinos, and photinos), the inferred solar abundances are too small by three to four orders of magnitude to solve the solar neutrino problem. Extreme fine tuning, marginally possible in the case of the photino, could increase solar abundances to a level where the neutrino signature would be affected. Otherwise, either a particle with a net cosmological asymmetry, or else a new mechanism for strengthening the existing Majorana suppression of s-wave annihilation at very low energies, would seem to be required.
142 citations
TL;DR: For neutrino mass eigenstates v i of mass between 0.5 and 1.75 GeV, it was shown in this article that neutrinos can be produced through mixing in charmed D meson decays.
126 citations
TL;DR: The hadronic contribution to the muon anomaly arising from diagrams containing hadronic light-by-light scattering subdiagrams using two different models is evaluated, with a result that disagrees with an earlier calculation.
Abstract: We have evaluated the hadronic contribution to the muon anomaly arising from diagrams containing hadronic light-by-light scattering subdiagrams using two different models. Our result is 49(5) x 10/sup -11/ which disagrees with an earlier calculation. We have also improved the contribution of the hadronic vacuum polarization diagrams to second- and fourth-order QED diagrams, using the latest experimental data. The results are 707(19) x 10/sup -10/ and -90(5) x 10/sup -11/, respectively. The complete hadronic contribution is thus 703(19) x 10/sup -10/. The remaining error comes predominantly from the experimental inputs needed for evaluating the hadronic vacuum polarization effect.
124 citations
TL;DR: In this article, the solar evolutionary consequences of both imposed isothermal core models and models including energy transport by a specific class of weakly interacting particles were explored, and a relative mass fraction, 10/sup -8/, of 4GeV particles was shown to reduce predicted neutrino count rates by more than a factor of 3.
Abstract: If the Sun contained even a small mass fraction of weakly interacting massive particles, there could be significant effects on central solar structure. The long mean free paths associated with such particles make them very efficient energy conductors. Consequently, an essentially isothermal core can be produced, which removes the central temperature peak responsible for the bulk of the predicted solar neutrinos in Davis's /sup 37/Cl neutrino capture experiment. We explore the solar evolutionary consequences of both imposed isothermal core models and models including energy transport by a specific class of weakly interacting particles. In particular, a relative mass fraction, 10/sup -8/, of 4GeV particles reduces predicted neutrino count rates by more than a factor of 3.
TL;DR: In this article, a new mechanism of quark and lepton mass generation via their mixing with hypothetical superheavy fermions is discussed for the model with the SU(5) ⊗ SU(3) H symmetry.
TL;DR: In this paper, the energy loss rates due to pair, photo-, and plasma neutrino processes are calculated in the framework of the Weinberg-Salam theory for wide ranges of densities and temperatures.
Abstract: The energy loss rates due to pair, photo-, and plasma neutrino processes are calculated in the framework of the Weinberg-Salam theory for wide ranges of densities and temperatures. Accurate analytic fitting formulas are presented to facilitate the application of the result. It is found that the present calculation gives a neutrino energy loss rate which is substantially lower than that of Beaudet, Petrosian, and Salpeter (1967). The reduction factor alpha is in the range 0.35-0.88 depending on the neutrino masses, density, and temperature. 13 references.
TL;DR: It is shown that qualitative agreement with the experiment can be obtained by taking into account the momentum (Fermi motion) and the energy distributions of nucleons in nuclei.
Abstract: We study the European Muon Collaboration effect within the conventional nuclear theory using the free-nucleon structure function. It is shown that qualitative agreement with the experiment can be obtained by taking into account the momentum (Fermi motion) and the energy distributions of nucleons in nuclei.
TL;DR: In this article, the neutrino-oscillation hypothesis and the standard solar model were tested using a large heavy-water Cherenkov detector, sensitive to neutrinos from /sup 8/B decay via the neutral current reaction and the charged current reaction.
Abstract: A direct approach to resolve the solar-neutrino problem would be to observe neutrinos by use of both neutral-current and charged-current reactions. Then, the total neutrino flux and the electron neutrino flux would be separately determined to provide independent tests of the neutrino-oscillation hypothesis and the standard solar model. A large heavy-water Cherenkov detector, sensitive to neutrinos from /sup 8/B decay via the neutral-current reaction ..nu..+d..--> nu..+p+n and the charged-current reaction ..nu../sub e/+d..-->..e/sup -/+p+p is suggested for this purpose.
TL;DR: In this article, general expressions for single and pair production cross sections of excited leptons are presented for a realistic SU(2)×U(1) invariant model.
Abstract: General expressions for single and pair production cross sections of excited leptons (e
*,µ*,v
*) are presented. Specific results are shown for a realisticSU(2)×U(1) invariant model. Pair production ine
+
e
− annihilation can measure anomalous magnetic moments of excited leptons. Single production ofe
* is dominated by thet-channel γ exchange contribution which makes its detection feasible up to masses just below thee
+
e
− c.m. energy. Due to this small |t| enhancement effect, contributions from elastic and resonance scattering inep production ofe
* are substantial. Realistic estimates of the excited lepton production cross section at HERA are given
TL;DR: In this article, the suppression of point-like configurations in bound nucleons, which can well explain the EMC effect at x > 0.3, leads to small nucleon swelling, small (∼ 3%) non-nucleon components in the nucleus wave function, noticeably increases the magnetic moment of the deuteron.
TL;DR: This work updates the calculation of the decays of the tau lepton into various modes using recent data on electron-positron annihilation into hadrons plus bounds that follow from isotopic-spin conservation.
Abstract: We update the calculation of the decays of the \ensuremath{\tau} lepton into various modes using recent data on electron-positron annihilation into hadrons plus bounds that follow from isotopic-spin conservation. Comparison is made with exclusive branching-ratio data and inclusive charged-prong-distribution measurements in \ensuremath{\tau} decays, and the difficulty in accounting for all the one-charged-prong decays as a sum of exclusive decay modes is discussed.
TL;DR: In this article, a measurement of the production of muon pairs in 194 GeV/c π−tungsten interactions is presented, where a sample of 155,000 events with mass higher than 4.07 GeV /c2 has been used to determine the differential cross-section as a function of the scaling variables.
Abstract: We present a measurement of the production of muon pairs in 194 GeV/c π−-tungsten interactions. A sample of 155,000 events with mass higher than 4.07 GeV/c2 has been used to determine the differential cross-section as a function of the scaling variables\(\sqrt \tau \) andxF.
TL;DR: In this article, the one-loop electroweak radiative corrections to the longitudinal polarization asymmetry and forward-backward asymmetry were calculated on and off Z 0 resonance in a renormalization scheme which uses τ e.m. (0), M Z, H H, M fermions and μ μ (the muon decay lifetime) as input data.
TL;DR: The measurements were performed to search for evidence of a beta-decay branch with a heavy neutrino, and the limit for the branch to a 17-keV neutrinos is 0.4%, in serious disagreement with the 3% branch claimed by Simpson.
Abstract: We present results of an experimental study of the shape of the energy spectrum for the decay /sup 35/S..-->.. /sup 35/Cl+e/sup -/+..nu../sub e/. The measurements were performed to search for evidence of a beta-decay branch with a heavy neutrino. No evidence for heavy neutrinos is observed. In particular, our limit for the branch to a 17-keV neutrino is 0.4%, in serious disagreement with the 3% branch claimed by Simpson.
TL;DR: In this paper, the authors compare the results of the Drell-Yan model with the results obtained by the next-to-leading logarithm approximation in first order QCD.
Abstract: The differential cross-section for dimuon production by 194 GeV/c π− onW, as measured by the NA10 Collaboration, is compared with theoretical models. The wide kinematical range of the data, extending well above the ϒ resonances, provides the opportunity of a comparison with ‘realistic’ Drell-Yan models, i.e. with those allowing for scaling violation in the hadronic structure functions. The data in fact clearly indicate the failure of the ‘naive’ Drell-Yan model, while the available ‘realistic’ versions (leading logarithm approximation and next-to-leading logarithm approximation in first order QCD), although giving a better description of the data, still disagree in thexF and\(\sqrt \tau \) dependences of the cross-section at high dimuon masses. This disagreement is referred to here as ‘anomalous’ scaling violation. The dependence of the results on external inputs (nucleon and pion-sea structure functions) is analysed; it is shown that in the next-to-leading logarithm approximation the value 〈K〉=1.03±0.03 (stat.) can be obtained for the ratio experimental/theoretical cross-section.
TL;DR: In this paper, the authors used the infrared fixed-point structure of the SU(3) × SU(2) × U(1) renormalization group equations to derive predictions for the masses and mixings of heavy families in perturbatively unifiable grand unified theories.
TL;DR: A recent observation of a 17-keV neutrino in tritium beta decay can be incorporated into the standard model with just three light neutrinos and models with Majorons or familons are found to be attractive possibilities.
Abstract: A recent observation of a 17-keV neutrino in tritium beta decay can be incorporated into the standard model with just three light neutrinos. Constraints on neutrino masses suggest that the lepton mass matrices have an approximate global symmetry which results in two of the three neutrinos having masses near 17 keV. A prediction for the mixing angle in ..nu../sub e/..--> nu../sub tau/ oscillations is made. Cosmological constraints on the 17-keV neutrino are discussed. Models with Majorons or familons are found to be attractive possibilities.
TL;DR: The HERA ep collider as mentioned in this paper is an example of high energy esup(+-)p collisions with unique mass ranges, up to 180-200 GeV, which are possible in the detection of new particles (leptoquarks, leptons, quarks, SUSY particles, etc.).
TL;DR: In this article, the effects of a weak isoscalar vector boson Y coupled to the weak hypercharge current, and, alternatively, the effect of an isoscalar vector Boson YL coupled with the left-handed part of the weak Hypercharge current only, are investigated within the framework of an effective electroweak lagrangian theory incorporating W(Y) dominance.
TL;DR: It is shown that the molecular effects are crucial for accurately determining the neutrino mass from a tritium ..beta..-decay experiment.
Abstract: The $\ensuremath{\beta}$-decay energy spectrum which results from the decay of one of the nuclei in the ${\mathrm{T}}_{2}$ molecule has been computed. An accurate, explicitly correlated basis set was used to describe electronic states of both the parent and the daughter molecules, and effects of nuclear motion have been taken into account. All the channels which meaningfully affect the spectrum have been incorporated, including resonance and scattering channels. The spectra are presented for several neutrino masses. It is shown that the molecular effects are crucial for accurately determining the neutrino mass from a tritium $\ensuremath{\beta}$-decay experiment.
TL;DR: The Higgs-boson contributions in three classes of models are examined and it is found that they are potentially the dominant effect and severe limits on the spontaneous-symmetry-breaking scales and Yukawa couplings are found in some scenarios which have a separate scale for fermion masses.
Abstract: We study the second-order weak correction to the muon anomalous magnetic moment in alternative electroweak gauge theories. The gauge-boson contributions are constrained by low-energy weak-interaction phenomenology. We examine the Higgs-boson contributions in three classes of models and find that they are potentially the dominant effect. Contributions of lepton-number-violating Higgs-boson interactions are calculated and included in the analysis. Severe limits on the spontaneous-symmetry-breaking scales and Yukawa couplings are found in some scenarios which have a separate scale for fermion masses, including the standard model with more than one doublet and a left-right model which naturally explains small neutrino masses. Higgs-boson effects may be detectable when order-of-magnitude improvements are made in the measurement of the muon anomalous magnetic moment.
TL;DR: In this article, all possibilities of lepton and family nonconservation in the standard SU(3)×SU(2)×U(1) gauge model induced by the existence of new scalars which can couple to the standard leptons, with emphasis on masses, were analyzed.